Recalculation

Hello and thanks for help in advance.

I have a recertification period of 60 days. This is recurring until the client is no longer with us, so it could be 10 or 100 times. What I want to do is:

- In one column, have the date that client started.
-In next column, have the 60 day recert date, which is 60 days from start.
-Once that date is reached, that SAME column will display the next 60 day date, if the recert has been done. (Maybe a third column asking 'yes or no' if it has been done...if yes then recalculate the date.)

Again, thanks for the help!